Dietary sources that include the active form of vitamin D3 (cholecalciferol) are usually from animal origins such as beef liver, oily fish, mackerel, salmon, trout, tuna, sardines, cod liver oil, egg yolks and cheese.
Article source: https://www.huffingtonpost.co.uk/entry/your-vitamin-d-is-about-to-run-dry-experts-say-we-need-to-take-action-now_uk_63ff314ee4b0c253d34831ce